1. Field of the Invention
The present invention relates to a reciprocating vibration generator used for a mobile phone etc., more particularly relates to a reciprocating vibration generator having a reciprocating vibrating body.
2. Description of the Related Art
For example, a vibroacoustic converter disclosed in Japanese Patent Publication (A) No. 2002-263578 is provided with a sound generating vibration plate with an outside end fastened to a top end of a cylindrical case, a plate fastening the outside end to the bottom end of the case, two plate springs supporting a ring-shaped weight to be able to reciprocate up and down, a bottom yoke plate fastened to an inner circumferential surface of the ring-shaped weight, a disk-shaped permanent magnet fastened on this bottom yoke plate and magnetized in the vertical direction, an upper yoke plate fastened to a top surface of this disk-shaped permanent magnet, a cylindrical voice coil fastened to a bottom surface of a sound generating vibration plate and with a front end side fit into a gap between an outer circumferential surface of the disk-shaped permanent magnet and an inner circumferential surface of the ring-shaped weight, and a magnetic fluid adhering to a bottom surface of the bottom yoke plate and functioning as a shock absorber for the plate.
The magnetic flux emitted from a disk-shaped permanent magnet magnetized in the vertical direction becomes leakage magnetic flux oriented from the bottom yoke plate toward the plate, so the closer the bottom yoke plate to the plate facing it, the more the magnetic flux of the bottom yoke plate bridges to the plate and acts as a shock absorber so can prevent abnormal noise at the time of collision.
In the above vibroacoustic converter, collision of the bottom yoke plate forming the reciprocating vibrating body and the plate facing this can be absorbed by the magnetic fluid, but when mounting a vibroacoustic converter in a mobile phone, the reciprocating vibrating body shakes in a direction off from the vertical direction in the face of external impact force given from various directions to the vibroacoustic converter, so the pole pieces of the reciprocating vibrating body collide with the voice coil in the gap and invite damage to the windings of the voice coil etc.